"Sunday stone" is an artificial stone composed of calcium carbonate that formed on the walls of drainage pipes in some coal mines.[1][2] It is striped due to the differing levels of coal dust produced during the day and night shifts.[1] In some cases, a broader stripe is generated every seven days due to active mining not taking place on Sunday.[1] Broader stripes would also appear when work stopped for other reasons.[2] In one case, a broad stripe coincided with workers being given the day off to view a cockfight.[2] Breaks of more than a day would produce an even broader stripe, such as when Christmas fell on a Monday.[2]
The Sunday stone would over time block the drainage pipes necessitating their replacement.[1] Where mines have improved ventilation, reducing the level of coal dust in the air, Sunday stone has ceased to be formed.[1]
References
^ abcdePearn, John H; Gardner-Thorpe, Christopher (11 July 2013). "11 July 2013". Geological Society, London, Special Publications. 375: 269–278. doi:10.1144/SP375.22. Retrieved 17 July 2018.
^ abcdKennedy, Jim. "Sunday Stone". oum.ox.ac.uk. Oxford University Museum of Natural History. Retrieved 17 July 2018.
